1. Field of the Invention
This invention relates to the manufacture of edible food casings derived from animal hide collagen and particularly to an improved method of humidifying the casings to render them amenable to shirring.
2. The Prior Art
Artificial sausage casings made of collagen have achieved wide success as a synthetic substitute for edible natural casings in the processing of sausages.
In the manufacture of collagen casings, the casings are extruded from a slurry of comminuted bovine hide derived collagen in the form of continuous tubing. For convenience of handling and shipping, the artificial sausage casings are shirred, from lengths ranging from 40-80 feet to a compacted length of a few inches, e.g., 6-10 inches using shirring machines of the type generally used in the shirring of cellulosic sausage casings. Typical shirring machines are shown in U.S. Pat. No. 2,722,714 2,722,715, 2,723,301, 3,122,517, 3,222,192, and 3,451,827.
The extruded casings generally have moisture contents in the range of 15-20%. In order to shirr these casings and to utilize these casings at the time of stuffing by the meat processor, the casings require higher moisture contents, i.e., moisture contents in the range of 20-26%. When the moisture content of the collagen casings is below the aforementioned required ranges, the casings are brittle and will very often fracture during their use by the meat processor. Thus, when the casings are stuffed, twisted and linked by the meat processor, if the casings are not adequately humidified, splitting at the shoulder portion of the meat filled casing will occur during twisting to prepare sausage links. This phenomenon is referred to in the art as "linker breakage" and if the linker breakage exceeds 2-3%, the casings are unacceptable for use.
It is a practice in the cellulosic food casing art to raise the moisture content of the casings to render them amenable to shirring and stuffing by internally humidfying the casings while simultaneously lubricating the casing on a shirring machine by spraying a stream of water and a separate stream of lubricant onto the walls of the casing through the shirring mandrel. Humidification has been also accomplished by spraying water onto the shirring wheels or shirring belts and then causing these wheels or belts to contact the external surface of the casing. It has been proposed in these processes to add wetting agents in a proportion of from about 0.02-0.04% by weight of the solution to enhance the rate of wetting of the casing. It has also been suggested to humidify cellulosic casings after they have been shirred by spraying a mixture of water and lubricant over the surface of the shirred casing. The lubricants used in the mixture are generally aqueous emulsions of vegetable, animal or refined oils.
Although these humidification methods have been effective for the humidification of cellulosic casings, attempts to employ these methods for the humidification of collagen casings have not been entirely successful.